Hybrid multi-element tapered rotating tower

ABSTRACT

The specification discloses a rotating turbine tower. The tower rotates to maintain the turbine facing into the wind. This allows structural optimization. The tower structure is comprised of a leading edge and a trailing edge, with joining panels between the edge structures. The tower edges are the main structural components of the tower. The separation of the edges tapers to follow the thrust bending moment on the tower, reducing the need to taper material thickness. The tapering shape of the tower structure matches the primary edgewise moment distribution. The tower can be assembled on site from components, thereby facilitating transportation to the tower site. The material properties and shape can be selected based upon the tower maintaining a near constant orientation with the wind. This can save weight and costs. The tower architecture can be of differing shapes such as a triangle or a structure tapering at each end.

RELATED APPLICATION

This application is a continuation in part of application Ser. No.12/554,884, entitled “Hybrid Multi-element Tapered Rotating Tower” filedSep. 5, 2009 which is incorporated by reference in its entirety.

BACKGROUND TO INVENTION

1. Intended Use

The invention is an advantageous construction of a rotatable windturbine tower. The turbine includes the rotor and nacelle. The turbineis attached at the top of the tower and changes direction with therotation of the tower. The tower has a narrow profile in one dimensionand a broad profile in a second dimension. This shape, combined withbearings, allows the tower to change orientation in response to changesin wind direction, aligning the structure with the wind direction tooptimally carry the loads, and thereby reducing the weight and cost ofthe tower.

2. Related Technology

Wind powered turbines are known. Most of these turbines utilize astationary tower and the turbine rotates 360° in a horizontal plane atthe top of the tower.

Some attempts have been made to construct a wind turbine with a towerthat turns with the direction of the wind. See UK patent 780,381 whereina rotating tower is stabilized by 3 legs and the turbine and generatorare located at ground level. See also UK patent 10,194 wherein the toweris constructed to turn freely to the wind on two rollers or ballbearings, one being at the base of the girder framework and the otherimmediately under the “wind wheel” or wind turbine. The rollers or ballbearings under the wind wheel consist of an annular ring designed toprevent the girder framework from having any upward or side motion. Thegirder framework remains free to revolve by means of rollers attached tothe framework. To keep the girder framework or tower in an uprightposition the annular ring is provided with suitable eyes or holes andsecurely anchored to the ground by means of steel guy ropes or rods. Therotating truss tower was not aerodynamically shaped.

SUMMARY OF INVENTION

The specification discloses a tower structure having a wing like shapewherein the wing is set upright on its end, i.e., a narrow crosswindthickness, an expanding along-wind width and a long double taperingstructure along its height. Also disclosed is a tower structure having atriangular shape with height.

The tower structure may have a straight leading edge extending to theheight of the structure. The narrow leading edge faces the winddirection and minimizes wind entry or passage drag and turbulence. Thetower structure also contains a trailing edge similarly extending to thetop of the structure. The trailing edge may bow outward expanding thewidth of the structure part way up the height of the structure. Thetrailing edge may taper toward the leading edge proximate to the towerends. As used herein, the “upper tower segment” means that portion ofthe tower where the trailing edge tapers above the maximum outwardbowing of the trailing edge to the leading edge. A triangular shapedstructure discussed below merges the trailing edge into the leading edgeproximate to the top of the tower.

The leading edge may maintain a uniform longitudinal axis. The trailingedge may be configured in a bowed or kinked shape, i.e., the distancebetween the leading edge and trailing edge can vary along the height ofthe structure. The leading edge and trailing edge are the primary loadbearing elements of the tower that support the turbine weight andthrust.

The leading edge and trailing edge may be comprised of strong highmodulus material such as metal or composite material containing highstrength fibers, e.g. unidirectional glass or carbon fibers. The leadingedge/trailing edge may also be steel. The leading edge or trailing edgemay be in a half circular shape and comprise multiple and attachablesegments stacked on top of a lower segment. The stacked segments form avertical structure, i.e., the leading edge and trailing edge. Eachsegment can be designed and fabricated to carry calculated loads basedupon the segment's position in the structure. Although semi-circularshapes are illustrated, other shapes are possible. For example theleading edge may have an elliptical shape, and the trailing edge mayhave a flat shape for wind release.

The side panels of the structure may be comprised of double bias (DB)glass. Other materials that may be used include but are not limited toplastics, fiber reinforced plastics, or panels over diagonal framebracing. The panels may comprise fiber reinforced composite materialwherein the direction of fiber is oriented to the panel load. In oneexample, the panels may comprise aluminum panels covering steel diagonalframework. In another embodiment, the panels may comprise a fiberglassskin over a foam core. The side panels may be oriented to providejoining between the leading edge and trailing edge. The side panels mayalso be aerodynamically shaped both in height and width.

The tower rotates with changes in wind direction. The wind turbine isfixedly mounted to the top end of the tower. As used herein, the term“turbine” includes the rotor and the nacelle. The “nacelle” may includethe main rotor bearings, generator, gear box, and associated equipment.The yaw motor will be either at the mid tower collar and upper bearingassembly, or at the tower base. Rotation of the tower and turbine occursby operation of a lower rotation assembly (hereinafter “bottom bearingassembly”) mounted approximately at ground level and a upper bearingassembly attached to the tower below the turbine rotor blades andproximate to the maximum bowing or separation of the trailing edge fromthe leading edge (hereinafter “mid-tower”). Additional or alternativebearing assemblies may be utilized. An acceptable bearing assemblyincludes the ability to carry side loads and permit rotation of thetower in 360°.

The upper bearing assembly comprises an annular structure surroundingthe wing shaped tower structure. Activation of the yaw motor and therotation of the tower through operation of the lower and upper bearingassemblies causes the tower leading edge to continuously point into thewind. This in turn points the turbine, fixed to the top of the tower,into the wind thereby enhancing energy production.

A second outer annular structure (hereinafter “mid-tower collar”) maysurround the upper bearing assembly. This second structure may be theattachment for reinforcing and stabilizing guy wires, cables, or rodsextending from the tower to the ground. The guy wires may be anchoredinto the ground. There may be three or more guy wires. For example,three guy wires would be spaced at approximately 120° apart. The secondouter annular structure may also provide horizontal reinforcement forthe upper bearing assembly.

In another embodiment, the tower may be a triangular shape. The shape isnarrow at the top juncture with the turbine and has a broad base at thebottom. The trailing and leading edges may be joined by a horizontalcomponent at the tower bottom. A structural concept of the inventionincludes matching the thrust bending moment and taper. Therefore a towerwith mid level support will have a double taper, whereas a tower withonly a bearing assembly at the base (triangular shaped tower) will haveonly a single taper. The bearing assembly will be at ground level. Thebearing assembly may include a turn table revolving device. This caninclude a rotatable horizontal disk that supports the tower. A yaw motorlocated at ground level can be used to turn the tower into the wind.

SUMMARY OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate preferred embodiments of theinvention. These drawings, together with the general description of theinvention given above and the detailed description of the preferredembodiments given below, serve to explain the principles of theinvention.

FIG. 1 illustrates a side view of the tower structure componentincluding the leading edge and trailing edge. The leading edge isleaning into the wind. Also illustrated is the bottom bearing assembly,the upper bearing assembly and the mid tower collar for anchoring guywires or synthetic cables. The tower vertical axis of rotation is alsoillustrated. Also illustrated is the nacelle showing the approximatesize of the nacelle to the tower structure. This size may varyconsiderably. For example, the size of the nacelle would be larger if alarge diameter direct drive generator were used.

FIG. 2A illustrates a top down cross sectional view of the towerstructure showing one embodiment of the leading edge, trailing edge andthe side panels. Illustrated are top views of the leading edge 110 andthe trailing edge 120.

FIG. 2B illustrates a top view of a cross sectional perspective of amore elliptical tower structure.

FIG. 3 illustrates a side view of an alternate embodiment forming atriangle shape wherein a vertical leading edge is supported by astraight but angled trailing edge.

FIG. 4 illustrates the tower of FIG. 1 leaning into the wind whereinmultiple side panels are mounted between the leading edge and trailingedges. Panels are mounted on both sides of the tower structure. Thevertical axis of rotation is illustrated.

FIG. 5 is a top cross sectional view of the tower and the mid-towercollar, upper bearing assembly and the inner collar.

FIG. 6 is a side view of the double tapered tower wherein the leadingedge leans forward outside of the axis of rotation. The relationshipbetween the tower leading edge and the turbine blade is alsoillustrated.

DETAILED DESCRIPTION OF INVENTION

It will be appreciated that not all embodiments of the invention can bedisclosed within the scope of this document and that additionalembodiments of the invention will become apparent to persons skilled inthe technology after reading this disclosure. These additionalembodiments are claimed within the scope of this invention.

The contents of the section entitled Summary of Invention areincorporated into the Detailed Description of the Invention herein.

The construction of wind turbines and generation of electricity fromthese turbines has increased significantly in the last ten to twentyyears. Most of these turbines utilize rotating blades and a nacellecontaining a gear box and generator setting atop of a fixed positionedtower. The rotor and nacelle rotate atop of a stationary tower inresponse to changes in wind direction. This rotation may involveoperation of a yaw motor.

There has been a goal to increase the size of the wind turbines. Thisgoal encounters problems of transporting large structural componentsover land to the installation site. It also encounters problems withmaterials required to withstand wind loads from all directions and thecorresponding increase in weight and material costs.

The wind turbine tower is typically cylindrically shaped and made fromsteel. The tower may have a tapering shape along the vertical axis. Inother examples, the tower may have a derrick frame shape similar to farmwindmills. Neither design is aerodynamically shaped, i.e. designed toreduce wind resistance. Since the towers are fixed in place, it is notpossible to provide an aerodynamic or structurally efficient shape sincethe wind direction is variable. Factors of structural efficiency includebut are not limited to cost, shape, material, material configuration,overall weight, and functionality.

The invention subject of this disclosure teaches constructing a towerstructure from multiple pieces or segments (elements). Both the leadingedge and trailing edge may comprise a plurality of segments stacked ontop of a lower segment. The trailing edge may progressively bow awayfrom the linear leading edge. This may form a structurally efficientshape, i.e., the shape produces a substantially constant load upon theleading edge and trailing edge. The shape comprises a progressivelydimensioned space between the leading edge and the trailing edge. Theleading edge and the trailing edge of the tower are sometimescollectively termed herein as “structural edges”. The structural edgesare load carrying. The leading edge faces the on coming wind. Converselythe trailing edge is on the lee side of the tower. Rotation of the towerensures the structure maintains this orientation to the wind. Utilizingthis constant orientation, structural tower loads can be predicted basedupon varying wind speeds. This predictability can allow the fabricationof the tower segments tailored to the position of each segment. Thetower can be structurally optimized. Stated differently, each towersegment can be structurally efficient. Each segment can be designed tocarry a specific load, allowing for cost effective utilization ofmaterials (hereinafter termed “structural efficiency” or “structurallyefficient”). For example the structural segments, including attachmenthardware, of the leading edge will experience both compression load and,in high wind, tension loads. The trailing edge segments may more oftenexperience or be subject to compression loading. The segments can alsobe aerodynamically shaped based upon their position relative to thewind. It will be appreciated that the leading edge is designed to alwayspoint into the wind and the trailing edge points away from the wind. Theside panels are designed to remain parallel to the wind.

The segments can be in lengths that allow use of standard transportationmethods. As discussed elsewhere herein, the trailing edge segment(s) maybe sized to nest in the leading edge segment(s) (or vice versa) duringtransportation.

The invention subject of this disclosure teaches a tower that can rotatein reaction to changes in the wind. The tower can be designed to bestructurally efficient. The tower rotates with the turbine (includingthe nacelle). This allows the tower to be designed to decrease thetower's drag in the wind. More important, only the leading edge seestension from variable wind thrust, with the trailing edge seeing orbeing subject to corresponding compression. Therefore the materialschoice and placement can be optimized for each type of loading, therebyallowing reduction of high strength and high cost materials. Inaddition, the tapering width allows nearly uniform stress in these mainstructural members so their material is loaded efficiently, and the sidepanels need carry only modest amounts of shear and bending loads. Therecan be an overall weight savings from carrying the loads in thisefficient manner, i.e., “structurally efficient”, and transportationcosts can be reduced because the tower segments are both smaller andlighter.

Referencing FIG. 6, the tower has a vertical axis of rotation 950. Theaxis of rotation extends vertically upward from the bottom bearingassembly (proximate to the tower foundation 360 and pivot stalk 370) andthrough the middle of the upper bearing assembly 220. The tower can beconstructed to allow portions of the structure to extend outside theaxis of rotation. Particularly the leading edge may lean into thewindward direction. This is termed “leaning forward” or “leaning intothe wind”. It will be appreciated that the tower 100 is leaning to theleft and into the wind as shown by vector arrow 975 (representing winddirection). This configuration increases the distance between the towerleading edge and the plane of rotation of the turbine blades. Theprogressively dimensioned or increased distance between the towerleading edge 110 and the turbine blade 402 is illustrated by distance401. This minimizes potential for damage to the turbine blades bystriking the tower. It also decreases the moment distribution from rotorthrust that must be carried by the tower and its supports.

A downwind rotor (not shown) can extend from the trailing edge 120outside the axis of rotation 950. This position facilitates thegenerating of the necessary moment needed to steer the tower into achanged wind direction. The winged shape formed by the straight leadingedge and the kinked trailing edge (described below) may provide thenecessary moment to steer the tower into a changed wind direction. Inanother embodiment, a vane structure fixed to the trailing edge can beused.

In one embodiment of the invention, the tower load is carried by theleading edge 110 and the separate trailing edge 120. See FIG. 1. Thisallows the sides of the tower structure to be covered with a lowerstrength load bearing material, i.e., structurally efficient, as statedin the preceding paragraph and further discussed in relation to FIG. 2.The tower edges define the outline of the wing shaped tower structure100 illustrated in FIG. 1. The tower edges diverge at the tower midpoint (kinked or bowed separation of the leading edge and trailingedge). The tower edges merge together at the bottom of the structure andare attached to the bottom bearing assembly 210. Beneath the bottombearing assembly (not shown) are a pivot stalk 370 and a foundation 360.

In the embodiment illustrated, the leading edge 110 leans forward intothe wind. The leading edge is not vertical. The axis of rotation 950 isvertical. As illustrated in FIG. 1, the axis of rotation starts at thepivot stalk 370 and extends upward through the center of the upperbearing assembly 220.

In one embodiment, (not shown) a hinge component connects the bottom ofthe leading edge and trailing edge segments with the foundation or withthe bottom bearing assembly. Other placements of the bottom hinge arepossible. This configuration allows the tower to pivot on the hinge, andthe lowering of the tower (and turbine) to be placed on the ground forservicing or repair. It may be found advantageous to attach the hinge tothe leading edge, thereby ensuring that the turbine and blades will befacing downward when the tower is lowered. The trailing edge can also beattached with a hinge to the foundation or bottom bearing assembly.Accordingly the tower can be lowered using the leading edge hinge or thetrailing edge hinge, depending upon the component of the turbine to beserviced. A hinge also allows the tower to be assembled and thenelevated and secured in the vertical position for initial erection.

The tower edges also merge 240 beneath the attachment fixture or base350 for the turbine nacelle 351. The orientation of the tower depictedin FIG. 1 to the wind direction is shown by vector arrow 975. The towermay be rotated in response to changes in the wind by use of a yaw motoror other device. Also illustrated is the progressively dimensioned space136 between the leading and trailing edges. It is this space that iscovered by the secondary load bearing material. See FIGS. 2 and 4.

See FIG. 2A comprising a cross-sectional top view of the towerstructure. Illustrated are the leading edge 110 and trailing edge 120,side panels 135 and the narrow profile of the tower structure facing thewind 975. The leading edge defines the narrow profile.

Referencing FIG. 1, because the tower edge separation profile is similarto the linear moment profile from rotor thrust, loads in the leading andtrailing edges are fairly constant and therefore a good match to aconstant material cross-section. Related to this is that primarystructural shear in the side panels and fasteners is low. The sidepanels may be a composite material. There will be kick loads at the kink130 in the trailing edge load path, but the mid-tower collar 230 may beinstalled at this location and may reinforce the trailing edge. Alsointerior structure such as wide flanges or a bulkhead integrated intothe joining of upper and lower tower sections may be used to react tothese kick loads. Further, operating fatigue loads in the tower,bearings, cables, and foundation are reduced by positioning the windturbine mass 350, 351 upwind of the rotating wind turbine tower axis ofrotation. The wind turbine mass may comprise the rotor blades, turbinerotor, nacelle, yaw motor and housing.

In the embodiment illustrated in FIG. 1, the structural edges achievemaximum divergence approximately in the midpoint 130, 131 of thestructure 100, i.e., mid-tower. This forms a maximum kink or widestbowed portion of the wing shaped tower structure. A upper bearingassembly 220 reacts the net loads from the two edges at or near thiswidest point. The upper tower section is above the upper bearingassembly. Of course, this upper bearing assembly facilitates therotation of the tower structure. The bearing assembly comprises anannular structure surrounding the wing shaped tower structure 100. SeeFIG. 2A for a top cross sectional view of the tower structure and theposition of the leading edge and trailing edge. Also illustrated in FIG.2A is the narrow profile of the wing shaped tower. This narrow profile,combined with the design of the tower leading edge and trailing edge,minimize wind resistance of the tower and thereby lessens the load uponthe tower components.

A second outer annular structure (mid-tower collar) 230 surrounds theupper bearing assembly 220. This mid-tower collar may be the attachmentfor guy wires, cables, or rods 310 extending to the ground that restrainthe tower structure at the point of greatest separation 141 (kink orbowed separation) between the load bearing leading edge 110 and trailingedge 120. One embodiment may incorporate a kink design in the leadingedge to facilitate the turning of the tower in response to changes inwind direction by moving tower steering area downwind of the towerrotation axis. Another embodiment comprises placing a downwind rotorsubstantially downwind of the tower rotation axis. In anotherembodiment, the turbine is turned by use of a yaw motor.

In one embodiment, side to side tower stiffness may be increased byadding brace wires or rods that extend from the tower top and bottom tothe mid tower bearing assembly. These wires or rods lie in a planeperpendicular to the leading edge to trailing edge plane, and attachnear the perimeter of a mid-tower inner collar and rotate with it. Thewires or rods extend from the top of the tower along a first side to thetower bottom and similarly extend along the second tower side. Theywould also attach to and rotate with supplemental bearing inner collars,if any are fitted below the upper bearing.

With reference to FIG. 2A, the leading edge 110 is illustrated tocomprise a half circle with a radius. The trailing edge 120 is alsoillustrated to be a half circle with a radius. The leading edge andtrailing edge carry the tension and compression load of the structure,including the rotor and nacelle weight. The leading and trailing edgesmay comprise steel having a high modulus of elasticity. The radius ofthe trailing edge can be smaller than the radius of the leading edge.Conversely, the radius of the leading edge can be smaller than thetrailing edge. This configuration allows the trailing edge to be storedwithin the leading edge for transportation (or vice versa).

The half circle shape enhances the load bearing capacity of the steel,in contrast to an equal thickness of sheet steel, because the curvedshape provides self stability against buckling. Continuing to referenceFIG. 2B, the top cross sectional view shows a tower embodiment having amore elliptical shape. Other embodiments can include a leading edge ortrailing edge having a parabolic shape or a shape tapering to a wider ornarrower crosswind dimension.

In addition to the leading edge 110 and trailing edge 120, FIGS. 2A and2B illustrate a third element of the tower, i.e., panels 135 that coverthe tower sides. These panels may cover both sides of the tower,creating a hollow interior space 136. The panels are attached to theleading edge and the trailing edge. FIGS. 2A and 2B illustrate onemethod of attachment wherein the panel 135 fits underneath the side edge137 of the leading edge 110. Conversely, the side panel fits over 138the side edge of the trailing edge 120. The attachment mechanisms can bebolts, screws or clips and are loaded in shear, i.e., the attachmentmechanism primarily tries to slide laterally in contrast to being pulledapart. A primary structural or sealant bond may be optionally provided.

The attachment method described above, i.e., the leading edge fittingover the side panel and the side panel fitting over the trailing edgeand in line with the air flow, advantageously minimizes debris andmoisture blowing into the joints or hollow space 136 of the tower. Thewind direction is illustrated by vector arrow 975. This attachmentmethod also reduces drag on the tower. The leading edge 110 is pointinginto the wind.

The side panels will experience in-plane, shear and air loads. Thesesecondary loads may be significantly less than the loads of the leadingand trailing edges. Accordingly, the side panels may be fabricated oflightweight secondary material. This, of course, reduces the weight ofthe tower. Side panel materials may include but are not limited tofiberglass, balsa or foam core within fiberglass skin panels, fiberreinforced plastics or non reinforced plastic. A diagonal metal framestructure with metal covering may also be used. The panels may be lowercost materials relative to the material used for the tower edges. Thepanel surface area will be subject to the force of a changed winddirection. This pressure on the bowed surface spanned by the panels mayprovide the moment to return the leading edge into the new winddirection.

The leading edge 110 will experience both compression and tensile loads.The compression load comes from the weight of the rotor and nacelle. Thetensile force will arise from, at least in part, the thrust action ofthe wind on the turbine rotor blades. When the leading edge is directedinto the wind with the turbine operating, there will be thrust inducedbending, simultaneous with compression from carrying weight (mass) fromthe turbine rotor, nacelle and housing. The leading edge must carry thenet resultant of these compression and tension loads. The trailing edge120 will experience compression from the thrust force and from theweight load, and must be stable against buckling. Due to the disparityof these forces and that the tower components are fabricated as separatepieces or segments, the leading edge may be made thinner than thetrailing edge (or vice versa), thereby saving on material andtransportation costs.

The lower portion of the tower (below the upper bearing assembly) seesmore compression than the upper tower portion due to the load from theanchored and tensioned guy wires. Again, since the tower segments may befabricated separately, the thickness of the tower leading edge andtrailing edge can be greater below the upper bearing assembly.

FIG. 3 illustrates another embodiment of the tower 100. The towerleading edge 110 may be vertical. The trailing edge 120 slopes in alinear fashion from the junction 240 with the leading edge. Thisjunction supports the nacelle or rotor attachment fixture 350. The towerenjoys a wider base 371 resting on a ring bearing 171 and a foundation360. Wires or rods that extend from the top of the tower to the bottombearing and add sideways strength and stiffness may be used with thisembodiment as well.

Illustrated in FIG. 3 are rotating mechanisms 171A, 171B, i.e.,turntable bearings, turning on the edge of the tower 100 allowingrotation of the tower within the base. Also illustrated is a yaw motor212 to power the rotation. The leading edge and the trailing edge areconnected by a horizontal frame component 211. The relationship of theleading edge to the wind is illustrated by vector arrow 975 representingthe wind direction. Side panels again join the leading and trailingedges in this embodiment. The force of changing wind direction on thepanel surface may provide the moment to rotate the leading edge into thenew wind direction, if the tower leans away from the wind instead ofinto is as shown.

In an alternative embodiment, the tower may rotate on a turntablecomponent. This may comprise a horizontal rotating plate mounted on thefoundation. The tower base would be attached to the plate or diskcomponent.

In another embodiment, a downwind rotor (not shown) is attached to thedownwind end of the nacelle, which is still mounted on top of the tower.The downwind rotor provides the mechanism for rotating the tower inresponse to changes in wind direction. The downwind mounted turbinerotor helps orient the leading edge into the wind. The downwind rotorwould be mounted sufficiently distant from the tower vertical axis ofrotation to provide the yaw alignment forces. The leading edge may slant(lean) downwind or be oriented into the wind. The trailing edge may bevertical or also slant downwind, to aid the downwind placement of theturbine.

The ability to choose the thickness, shape, and local radius ofcurvature of the trailing edge part enhances the buckling stability ofthe trailing edge while minimizing its weight and cost, i.e., structuralefficiency. Similarly, these characteristics could be varied for theleading edge as a function of height to minimize weight and cost. Thethickness of the tower i.e., the separation between side panels, couldalso be varied with height if this provides lower weight and cost, byvarying the edge to edge crosswind width dimensions of the leading andtrailing edge pieces.

FIG. 4 illustrates the leaning tower structure 100 depicted in FIG. 1with the addition of the side panels 135 spanning the space 136 betweenthe leading edge 110 and trailing edge 120. The side panels need carryonly lesser amounts of shear and bending loads. The vertical axis ofrotation is shown extending from the pivot stalk 370 and through themiddle of the mid tower collar 230. It extends outside the towerstructure. FIGS. 2A and 2B illustrate an embodiment of attaching theside panels to the leading and trailing edges.

Also illustrated are the mid-tower collar 230 and guy wires 310, thetower structure midpoints 130,131 and the bearing assembly 220. Alsoillustrated is the merging of the leading and trailing edges 240, thenacelle attachment component 350, the bottom pivot post 370, thefoundation 360.

FIG. 5 illustrates an embodiment for supporting the tower and allowingthe tower to rotate. Illustrated is a top cross sectional view showingthe tower comprising the leading edge 110, the side panels 135, and thetrailing edge 120. The tower edges carry rotating bearings 170A thru170D or similar components that are in contact with the circular surface220 of the bearing assembly. Also illustrated are three guy wires orrods 310A, 310B, 310C, attached to the mid tower collar 230. Also shownis the space 136 between the tower edges 110, 120. The mid-tower collarsurrounds the upper bearing assembly and provides structural restraint.

The tower structure 100 may also include an inner collar 221. Thiscollar 221 can be a flat plate surrounding the tower and attached to itat or near its widest point. The inner collar rotates with the towerwithin the upper bearing assembly. In FIG. 5, the area between thebearing assembly 220 and tower 100 is filled with a planar structure,possibly made from a flat plate, or plate with holes to make it lighter.The bearings may be in a few discrete locations as shown, or distributedmore widely around the inside perimeter of the upper bearing assembly220. In one embodiment, the bearings are external to the towerstructure, i.e., “external bearing assembly”. The inner collar stops thetower from deforming out of shape at the kink. Alternatively, a planarstructure on the inside would restrain the shape and achieve the sameresult.

This specification is to be construed as illustrative only and is forthe purpose of teaching those skilled in the art the manner of carryingout the invention. It is to be understood that the forms of theinvention herein shown and described are to be taken as the presentlypreferred embodiments. As already stated, various changes may be made inthe shape, size and arrangement of components or adjustments made in thesteps of the method without departing from the scope of this invention.For example, equivalent elements may be substituted for thoseillustrated and described herein and certain features of the inventionmay be utilized independently of the use of other features, all as wouldbe apparent to one skilled in the art after having the benefit of thisdescription of the invention.

While specific embodiments have been illustrated and described, numerousmodifications are possible without departing from the spirit of theinvention, and the scope of protection is only limited by the scope ofthe accompanying claims.

1. A rotating wind turbine tower comprising: a) a leading edge and atrailing edge that carry the primary tower tension and compression loadsfrom a turbine, nacelle, and rotor thrust induced bending; b) astructurally efficient, progressively dimensioned space between theleading edge and the trailing edge that produces largely constant loadsin the leading edge and the trailing edge; and c) side panels joiningthe leading edge and the trailing edge.
 2. The rotating wind turbinetower of claim 1 further comprising the trailing edge having a maximumkinked or bowed separation from the leading edge proximate to an upperbearing assembly and tapering toward the leading edge proximate to eachtop and bottom tower end.
 3. The rotating wind turbine tower of claim 2wherein both the leading edge and trailing edge are kinked or bowed awayfrom each proximate to the upper bearing assembly.
 4. The rotating windturbine tower of claim 1 comprising a tower rotation axis passingthrough the center of an external upper bearing assembly locatedproximate to a widest separation of the leading edge and the trailingedge.
 5. The rotating wind turbine tower of claim 4 further comprising:a) a upper bearing assembly positioned at the kinked or bowed maximumseparation between the leading edge and the trailing edge; b) amid-tower collar surrounding the upper bearing assembly; and c) aplurality of guy wires attached to the mid-tower collar and extending tothe ground.
 6. The rotating wind turbine tower of claim 4 furthercomprising one or more additional bearing assemblies below the upperbearing assembly.
 7. The rotating wind turbine tower of claim 4 furthercomprising at least one brace wire or rod on one first side and on anopposite second side, attached and extending from a top tower end to abottom tower end, retained perpendicular to the leading edge to trailingedge plane, that attach to a upper bearing assembly and rotate with it.8. The rotating wind turbine tower of claim 1 further comprising atrailing edge extending upward linearly from a horizontal framecomponent attached to a bottom bearing assembly and the trailing edgehaving an angled relationship with the leading edge for the wholeheight, without a mid-tower kink or bulge.
 9. The rotating wind turbinetower of claim 1 further comprising the leading edge having a firstradius and the trailing edge having a second radius wherein one radiusis smaller than the other radius.
 10. The rotating wind turbine tower ofclaim 1 further comprising the leading edge and the trailing edge madeof metal, metal alloy, or composite material and the load bearing sidepanels comprising a cored composite material, composite sheet, ornon-structural sheet over frame work.
 11. The panels of claim 1 furthercomprising the leading edge overlapping the side panels and the sidepanels overlapping the trailing edge.
 12. The rotating wind turbinetower of claim 1 further comprising the leading edge, the side panels,and the trailing edge, and further comprising the turbine rotorextending downwind beyond the trailing edge.
 13. The rotating towerstructure of claim 1 comprising a hinge connected proximate to the towerbottom that allows raising the tower to vertical, or lowering it tohorizontal.
 14. A cable restrained rotating wind turbine tower comprisedof the leading edge leaning forward into the wind.
 15. The rotating windturbine tower of claim 14 whereby the upper tower portion leans forwardinto the wind and thereby increases the clearance of a wind turbinerotor blade to the leading edge of a cable restrained rotating windturbine tower.
 16. The rotating wind turbine tower of claim 14 wherebyoperating fatigue loads in the tower, bearings, cables, and foundationare reduced by positioning the wind turbine mass upwind of the rotatingwind turbine tower axis of rotation.
 17. A wind turbine tower thatrotates with changes in wind direction comprising a leading edge, atrailing edge, and side panels comprised of multiple segments and eachsegment maintaining the same orientation to the wind, and the segmentsare fabricated to carry tower loads specific to the segment's positionin the wind turbine tower, and to have aerodynamic shapes relative tothe wind.
 18. The wind turbine tower of claim 17 where the segments maybe of different materials or construction, with high strength materialson the primary load paths, and lighter or lower cost materials insecondary load paths.
 19. The wind turbine tower of claim 17 where theleading edge segments are shaped for low drag entry into an airflow;further comprising the side panels are shaped for low drag passage ofairflow across a side tower dimension, and trailing edge panels areshaped for desired release properties of the airflow
 20. The windturbine tower of claim 17 comprising leading edge, trailing edge andside panel segments that are dimensioned for one segment to nest withinor upon another segment.